This disclosure relates generally to wireless communication systems, and in particular but not exclusively, relates to an internal reflection apparatus and method using a holographic optical element (HOE) for a free space optical communication system.
With the increasing popularity of wide area networks, such as the Internet and/or World Wide Web, network growth and traffic have exploded in recent years. Network users continue to demand faster networks, and as network demands continue to increase, existing network infrastructures and technologies are reaching their limits.
An alternative to existing hardwire or fiber network solutions is the use of wireless optical communications technology. Wireless optical communications utilize beams of light, such as lasers, as optical communications signals, and therefore do not require the routing of cables or fibers between locations. Data or information is encoded into a beam of light, and then transmitted through free space from an optical transmitter to an optical receiver.
At a basic level, a typical optical receiver is basically a telescope having many components, including associated electronics to demodulate data on the light beam and to perform other processing. Because these optical receivers have many parts, their overall size or xe2x80x9cfootprintxe2x80x9d increases. The individual parts themselves may also have a large footprint. This increased footprint can be detrimental in situations where the units need to be installed in a non-obtrusive manner.
As an example, a problem with most through-the-window optical communication devices, such as optical receivers, is that they tend to take up window space. The larger the collector aperture of an optical receiver, the more light power can be collected, but at the cost of space. The large size of the optical receiver can significantly and undesirably obstruct a window, thereby blocking sunlight or blocking what may otherwise be a beautiful view.
The large size of these optical receivers also makes them heavy. This increased weight thus requires such optical receivers to be firmly and structurally supported, and makes them difficult to install, move, or reposition. The large number of parts of these optical receivers also contributes to their overall cost, including significant manufacturing expenses incurred since the complexity of the optical receivers may preclude cost-effective mass-production techniques.
According to an aspect of the invention, an apparatus includes an element having a front surface and a back surface. A holographic optical element (HOE) is disposed to angularly direct a light signal towards one of the surfaces of the element to allow the light signal to propagate between the front and back surfaces of the element via internal reflection.